Class 11th Statistics Collection of Data Notes

1. Sources of Collection of Data

• Primary Data:
  Data collected by the investigator himself for the first time for a specific purpose.
  Example: Data collected through surveys, interviews, observations.
• Secondary Data:
  Data already collected by someone else and used by the investigator for reference.
  Example: RBI publications, Census reports, NSSO data.

2. Nature of Data

• Primary Data: First-hand, original data collected for the current investigation.
  Example: Conducting a survey of students to know their study hours.
• Secondary Data: Second-hand data, already collected for some other purpose.
  Example: Using government census data for population study.

3. Difference Between Primary and Secondary Data

4. Statistical Methods / Modes of Collection of Data

(i) Personal Interviews

(a) Direct Personal Investigation

• Definition: Investigator personally collects information from the informants.
• Suitability: Best for small-scale, local, and intensive studies.
• Advantages:
  1. Original and accurate data.
  2. Highly reliable.
  3. Clarifications possible.
  4. Investigator observes personally.
  5. Control over data collection.
• Disadvantages:
  1. Very costly.
  2. Time-consuming.
  3. Difficult in large areas.
  4. Needs trained investigators.
  5. Subject to personal bias.

(b) Indirect Oral Investigation

• Definition: Data collected from third parties or witnesses instead of directly from informants.
• Suitability: Best for sensitive issues or when direct contact is not possible.
• Advantages:
  1. Cheaper than direct method.
  2. Less time required.
  3. Wide coverage possible.
  4. Useful in confidential matters.
  5. Easy to conduct.
• Disadvantages:
  1. Less reliable.
  2. Depends on others’ statements.
  3. May lack accuracy.
  4. Difficult to verify truth.
  5. Biased answers possible.

(c) Information from Local Sources / Correspondents

• Definition: Data collected regularly from local agents or correspondents appointed in different areas.
• Suitability: Best for continuous information like newspapers, trade journals, weather reports.
• Advantages:
  1. Continuous flow of data.
  2. Wide area coverage.
  3. Quick availability.
  4. Low cost.
  5. Useful for journals and agencies.
• Disadvantages:
  1. May lack accuracy.
  2. Reports may be biased.
  3. Delay possible.
  4. Investigator has little control.
  5. Reliability doubtful.

(ii) Information Through Questionnaires or Schedules

(a) Mailing Surveys (Questionnaires)

• Definition: List of questions sent by post to respondents for replies.
• Suitability: Best when respondents are educated and spread over a wide area.
• Advantages:
  1. Covers large area.
  2. Low cost.
  3. Respondents answer at convenience.
  4. No interviewer bias.
  5. Suitable for large-scale surveys.
• Disadvantages:
  1. Low response rate.
  2. Only literates can respond.
  3. Delay in response.
  4. Clarifications not possible.
  5. Incomplete or careless answers.

(b) Enumeration Method (Schedules)

• Definition: Enumerators personally visit respondents and fill the schedule.
• Suitability: Best when respondents are illiterate or when detailed information is required.
• Advantages:
  1. Reliable and detailed data.
  2. Clarifications possible.
  3. High response rate.
  4. More accuracy.
  5. Suitable for all sections of society.
• Disadvantages:
  1. Very costly.
  2. Time-consuming.
  3. Requires trained staff.
  4. Personal bias possible.
  5. Difficult for large geographical areas.

(iii) Telephonic Interviews

• Definition: Information collected by asking questions over the telephone.
• Suitability: Best for quick information where personal contact is difficult.
• Advantages:
  1. Quick method.
  2. Saves time and money.
  3. Wide coverage.
  4. Respondents feel comfortable.
  5. Easy for preliminary surveys.
• Disadvantages:
  1. Limited number of questions possible.
  2. Only people with telephones can be contacted.
  3. Respondents may refuse to cooperate.
  4. Less reliable than personal interviews.
  5. No personal observation possible.

5. Collection of Secondary Data

• Published Sources: Data already collected and made public by different organizations.
  Examples:
  1. Census Reports – Population and demographic details.
  2. Economic Surveys – Annual government survey.
  3. RBI Publications – Banking and finance data.
  4. UN Reports – International statistics.
  5. Trade Journals & Magazines – Industry and market data.
• Unpublished Sources: Data not published but available in records.
  Examples:
  1. Company Records – Sales, production, accounts.
  2. Research Theses – University projects.
  3. Government Departments’ Internal Files – Confidential data.
  4. Private Institutions’ Surveys – NGO studies.
  5. Committee Reports – Investigations by commissions.

6. Precautions in the Use of Secondary Data

1. Check reliability of the source.
2. Data must be suitable for the study purpose.
3. Ensure definitions and methods are clearly understood.
4. Units of measurement must match requirements.
5. Data should be recent and up to date.

7. Two Major Sources of Secondary Data

1. Census of India
   • Conducted every 10 years by the Government of India.
   • Provides reliable data on population, literacy, housing, employment, migration, etc.
2. NSSO (National Sample Survey Organisation)
   • Conducts sample surveys on socio-economic aspects like consumption, health, education, employment.
   • Supplements census data with frequent and detailed studies.